Method for Verifying a Pattern of Features Printed by a Lithography Process

1. A method for verifying a printed pattern of features printed through a lithographic mask, the printed pattern approximating a reference pattern, the method comprising: defining sectors of at least a portion of the features in the reference pattern; producing a lithographic mask according to a mask design suitable for printing an intended pattern; printing a pattern through the lithographic mask; determining a contour of the printed pattern; superimposing the contour of the printed pattern on the reference pattern; determining surface areas of sectors of the printed pattern that correspond to the sectors of the reference pattern; calculating one or more parameters as a function of at least one of the surface areas, the parameters being related to a single sector or to multiple sectors, wherein one of the parameters is a ratio of the surface area of a sector of the printed pattern to a surface area of a corresponding sector of the reference pattern; and evaluating the parameters with respect to a reference value.

2. The method according to claim 1 , wherein the reference pattern is a design intent pattern used for designing the lithographic mask.

3. The method according to claim 1 , wherein the reference pattern is a contour of a simulated pattern.

4. The method according to claim 1 , wherein the reference pattern comprises one or more line-shaped features, and wherein the line-shaped features are subdivided into sectors by defining line-end sectors, corner sectors and line sectors.

5. The method according to claim 1 , wherein the sectors of the reference pattern and the corresponding sectors of the printed pattern are defined by defining one or more regions comprising two or more neighbouring sectors of features in the reference pattern and of the corresponding features in the printed pattern, and wherein for each of the defined regions the steps are performed of: determining the surface area R of the region; determining R-R′, with R′ the total surface area of the two or more neighbouring sectors of the printed pattern; determining R-R″ with R″ the total surface area of the two or more neighbouring sectors of the reference pattern; and calculating a ratio (R-R′)/(R-R″) as one of the parameters.

6. The method according to claim 1 , wherein the one or more parameters are determined on a plurality of versions of the printed pattern, the versions being printed in a lithographic tool wherein a focus and/or a dose is varied in the plurality of versions, and wherein one or more process windows are determined from the values of the parameters.

7. A method for verifying a printed pattern of features printed through a lithographic mask, the printed pattern approximating a reference pattern, the method comprising: defining sectors of at least a portion of the features in the reference pattern; producing a lithographic mask according to a mask design suitable for printing an intended pattern; printing a pattern through the lithographic mask; determining a contour of the printed pattern; superimposing the contour of the printed pattern on the reference pattern; determining surface areas of sectors of the printed pattern that correspond to the sectors of the reference pattern; calculating one or more parameters as a function of at least one of the surface areas, the parameters being related to a single sector or to multiple sectors; and evaluating the parameters with respect to a reference value, wherein the reference pattern comprises one or more line-shaped features, and wherein the line-shaped features are subdivided into sectors by defining line-end sectors, corner sectors and line sectors, wherein the line-shaped features are designed for producing a pattern of metal lines in a level of an integrated circuit, with via connections above and/or below the pattern, the via connections overlapping a line-end, a line or a corner of the pattern, and wherein the definition of at least some of the line-end sectors, line sectors and corner sectors takes into account the dimensions and position of via connections overlapping the sectors, as well as an overlay error between the metal line pattern and the via connections.

11. A method for designing a lithographic mask, comprising: providing an intended pattern comprising a plurality of structural features; producing a mask design of a lithographic mask suitable for printing the intended pattern, and one or more simulated patterns printed through the mask design; producing a lithographic mask according to the mask design; printing a pattern through the lithographic mask; and performing a verification of the printed pattern, wherein the verification comprises: defining sectors of at least a portion of the features in a reference pattern, with the intended pattern or one of the simulated patterns serving as the reference pattern; determining a contour of the printed pattern; superimposing the contour of the printed pattern on the reference pattern; determining surface areas of sectors of the printed pattern that correspond to the sectors of the reference pattern; calculating one or more parameters as a function of at least one of the surface areas, the parameters being related to a single sector or to multiple sectors; and evaluating the parameters with respect to a reference value.

12. The method according to claim 11 , further comprising: updating the mask design on the basis of the verification; producing a second lithographic mask according to the updated mask design; printing a pattern through the second mask; and performing a further verification on the pattern printed through the second mask, wherein the preceding steps are repeated until a lithographic mask is produced that answers to a pre-defined set of requirements in terms of a difference between the printed pattern and a reference pattern.

13. The method according to claim 11 , wherein producing a mask design suitable for printing the intended pattern and producing one or more simulations of the printed pattern is performed by using a software tool for optical proximity correction.

14. The method according to claim 13 , wherein the step of determining, on the contours obtained from the printed pattern, the value of one or more of the parameters, is performed by using the OPC software tool for verifying the contours.